Compositions of biotite from granitoids of the Sierra Nevada batholith: constraints on magmatic source rocks

Conference · Tue Jan 01 00:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6685604

Ague, J J; Brimhall, G H

Two compositional types of biotite from the Cretaceous Sierra Nevada batholith occur in a systematic regional pattern which reflects magmatic source material and correlates with tungsten mineralization. Biotite from each group may be characterized in terms of F/OH and Mg/Fe as follows. Type I biotites generally coexist with hornblende and magnetite + sphene. Type II biotites coexist with ilmenite +/- magnetite, but hornblende only occurs at contacts with Type I intrusives. Intrusives with Type IA biotite occur as a continuous belt along the entire western margin of the exposed batholith. Type IB biotite is found to the east of this belt, and Type IC biotite is confined to the eastern side of the Sierra. Type II biotite is present in the eastern and south-western portions of the Sierra, and sporadically in the metamorphic foothills belt. The two intrusive groups, here characterized by biotite compositions, correspond to two of the source rock and porphyry mineralization models of Burnham (1981). Type I rocks (Cu deposits) are derived from mafic amphiobolites whereas Type II (Sn-W deposits) form from relatively reduced muscovite-rich metasediments. The biotite compositions indicate that the majority of the batholith formed from amphibolite sources. Type II intrusives and W deposits occur in areas underlain by Precambrian crust as defined by radiogenic isotope studies.

• Research Organization: Univ. of California, Berkeley (USA)
• OSTI ID: 6685604
• Report Number(s): CONF-8510489-
• Journal Information: Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
BIOTITE
PETROCHEMISTRY
PETROGENESIS
PLUTONIC ROCKS
CALIFORNIA
CHEMICAL COMPOSITION
CRETACEOUS PERIOD
MAGMATISM
MINERALIZATION
MINERALOGY
NEVADA
FEDERAL REGION IX
GEOLOGIC AGES
IGNEOUS ROCKS
MESOZOIC ERA
MICA
MINERALS
NORTH AMERICA
ROCKS
SILICATE MINERALS
USA
580400* - Geochemistry- (-1989)
580300 - Mineralogy
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& Rock Mechanics- (-1989)